Performance of a H_2/O_2 PEMFC with a Phosphotungstic Acid Treated Membrane

摘要

Resistive losses within proton exchange membrane fuel cells (PEMFC) result, in part, from the decrease of the membrane protonic conductivity as a consequence of partial dehydration. Impregnation of the membrane with phosphotungstic acid (PTA) decreases the dependence of the performance on humidification. In this work, the performance of PEMFC with Nafion~R membranes impregnated with phosphotungstic acid by several methods are discussed and compared with those obtained with non-impregnated membranes. The polarization curves of the cells with PTA impregnated membranes indicate a small increase in the activation losses caused by a poisoning effect on the electrode reactions, particularly the oxygen reduction reaction. This is compensated by a decrease of the linear and non-linear ohmic losses resulting from a decrease of the membrane resistivity and on the overall water dragging effect. Contrary to the conventional system, the performance of the cell with the impregnated membrane is stable for over 500 h of operation, for the reactant gases humidified at the same temperature than the cell.